Diffusion transfer photographic package with pressure-rupturable capsule of edge-sealing adhesive



June 14, 1966 J. H. BOOTH 3,256,090

DIFFUSION TRANSFER PHOTOGRAPHIC PACKAGE WITH PRESSURE-RUPTURABLE CAPSULE 0F EDGE-SEALING ADHESIVE Filed March 27, 1961 Z pIl/INVENTOR.

A R| \|EYS United States Patent 3,256,090 DIFFUSION TRANSFER PHOTOGRAPHIC PACK- AGE WITH PRESSURE-RUPTURABLE CAPSULE OF EDGE-SEALING ADHESIVE Joseph H. Booth, Belmont, Mass, assignor to Polaroid Corporation, Cambridge, Mass., a corporation of Dela- Ware Filed Mar. 27, 1961, Ser. No. 98,652 7 Claims. (CI. 96-29) The present invention relates to photography and, more particularly, to photographic processes and products that involve spreading a photographic processing composition in a thin layer between a photosensitive stratum and a printor image-receiving stratum.

In one process of this type, the processing composition is spread between a pair of sheets, one of which carries a photosensitive stratum, to provide what may be termed a sandwich. Spreading of the processing composition may be eifected by advancing the sheets, with the processing composition interposed, between a pair of pressure-applying rollers and into a dark chamber. Thereafter, the sheets are maintained in superposed relation for a predetermined processing period during which a visible print is produced from a latent image in the photosensitive stratum. At the completion of this processing period, the sheets are stripped apart to uncover the print. Ordinarily, the sandwich, during processing, is retained in the dark chamber for the purpose of preventing further exposure of the photosensitive stratum to environmental light before the processing period is completed. However, it has now been shown, for example in US. Patent No. 2,834,269, that the dark chamber can be eliminated and the camera simplified by advancing the sandwich directly from the rollers out of the camera. It is necessary, however, in this embodiment that the sandwich, once formed, be removed from the camera without danger of exposing the photosensitive stratum to environmental light before'the processing period is completed. Thus, the photosensitive stratum of the sandwich must be shielded or protected during the processing period by preventing environmental light from penetrating through the outer surfaces and edges of the sandwich. One effective and practical manner of preventing environmental light from penetrating through the outer surfaces of the sandwich is by employing opaque sheets or supports for carrying the photosensitive and image-receiving strata. Examples of such light barriers or shields may be found in copending US. application Serial No. 825,754, filed July 8, 1959, now abandoned. The effective and simple prevention of the penetration of environmental light through the edges of the sandwich has been somewhat more difficult and it is with this aspect that the present invention is concerned. Penetration of such light through the edges of the sandwich may result in the appearance of highlight streaks in the print. This is particularly so where the photosensitive stratum is of a high speed. The present invention is thus directed to scaling the edges of such a sandwich in a'manner as to substantially prevent the passage of light therethrough during the processing period.

The present invention, which is particularly applicable in conjunction with film packs such as shown, for example, in US. Patents Nos. 2,495,111 and 2,669,168, is also useful with sheet film or in photographic film uni-ts or assemblages such as shown, for example, in copending US. application Serial No. 820,266, now US. Pat. No. 3,047,387, filed June 15, 1959.

As it is understood to the art, a photographic transfer process may be carried out to form in an image-receptive stratum a reverse image of a latent image contained in an exposed silver halide photosensitive stratum. By one practice, a transfer process may be effected by spreading a viscous liquid processing composition between and in contact with an image-receiving layer or stratum and an exposed silver halide photosensitive layer or stratum which are arranged in superposed relation. The processing composition employed is one which is capable of developing a latent image in the photosensitive layer and of providing an imagewise distribution of image-forming components therein as a result of said development. These image-forming components are transferred in solution, and without appreciably disturbing said irnagewise distribution, from the photosensitive stratum to the imag -receiving stratum to provide the desired reverse image. At the end of a predetermined processing period the photosensitive stratum and image-receiving stratum are stripped apart to expose the positive image produced.

It is desirable to provide framing means in the form of a mask, preferably of a relatively thin flexible material, on the surface of the image-receiving stratum which is adapted to receive the transfer image. This mask is provided with an aperture adapted to define the picture area on the image-receiving stratum while the portions of the mask which surround the aperture restrict contact of the processing composition to the picture area and also confine the transfer image thereto. This mask is generally temporarily bonded or adhered to the surface of the image-receiving stratum so that the image-receiving stratum may be displaced from the mask in providing the finished positive print. At the same time, the bond between the mask and the image-receiving stratum-has sufficient strength to hold the mask on the stratum during handling, storage and use of the film.

The primary object of the present invention is to provide novel photographic processes and products involving elements or sheets characterized by an image-v receiving stratum or framing means therefor and/or a photosensitive stratum having marginal edge portions thereof coated with minute or microscopic pressurerupturable capsules of polymeric material containing therewithin one or more materials which, when released from said capsules, provide an adhesive or bonding material or composition adapted to seal together edge portions of such photosensitive and image-receiving strata or to seal together framing means and edge portions of a photosensitive stratum when brought into superposed relationship.

Another object of the invention is to provide novel photographic processes and products for obtaining images by difiFusion-transfer involving elements or sheets as described above.

Another object of the invention is to provide novel photographic processes and products for obtaining images by diffusion-transfer involving elements or sheets as described above wherein an adhesive is encapsulated within pressure-rupturable minute or microscopic capsules of polymeric material and anactivator therefor is encapsulated within other pressure-rupturable minute capsules, the two types of capsules being either interspersed and coated on the marginal edge portions of one of the abovementioned strata or means or maintained separately, that is, one type being coated upon the marginal edge portions of the photosensitive stratum and the other type being coated uponthe marginal edge portions of the' image-receiving stratum or framing means therefor, or one type being coated upon the marginal edge portions of one of said strata or means and the other type being overcoated thereon.

Still another object of the invention is to provide novel photographic processes and products for obtaining images by diffusion-transfer involving elements or sheets as described above wherein a coating containing an adhesive in inactive form is utilized and a liquid solvent or vehicle therefor to activate the adhesive is enclosed or encapsulated within pressure-rupturable minute capsules of polymeric material, the adhesive and liquid activatorcontaining capsules being coated separately or interspersed on the marginal edge portions of one of the abovementoned strata or means or carried separately upon the marginal edge portions of the photosensitive stratum and image-receiving stratum or framing means therefor.

Still another object of the invention is to provide photo- 1 graphic processes and products of the above types wherein a light-absorbing material is employed in conjunction with said adhesive.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the several steps and the relation and order of one or more of such steps with respect to each of the others, and the products possessing the features, properties and the relationof elements which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

Fora fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing which is a schematic perspective view of a typical product embodying the invention.

In the broadest sense, an adhesive is a material which can bond two other materials together by adhering to the surfaces of both. In other words, it is a material which is employed between two surfaces to make them cling or stick together. The terms adhesive or adhesiveforming material as used in the present specification and claims include within their scope bonding materials designated as cements, glues, pastes, plastic bonds, mucilages and the like. These terms thus include within their meanings adhesive materials which require no physical or chemical treatment to function, and materials which must be physically and/ or chemically treated by solvents, heat,

catalysts and the like before becoming effective bonding materials. The adhesives employed in the present invention are those well known in the art. For example, there may be employed pressure-sensitive adhesives, solventresponsive adhesives, chemically reactive adhesives and the like. The adhesive to be employed may be chosen so as to give temporary or substantially permanent bonding. Temporary bonding adhesives of the moisture releasable type which are employed for securing the framing means to the surface of the image-receiving stratum may also be employed in the instant application. The term moisture releasable as used herein is intended to signify the property of an adhesive whereby a consequential reduction of said adhesives bonding capacity occurs upon liquid permeation of said adhesive. Examples of such moisture releasable adhesives are disclosed in copending US. applications Serial No. 709,054, filed January 15, 1958, now abandoned, and Serial No. 748,890, filed July 16, 1958, now abandoned.

The invention broadly comprehends a novel product including a photographic element having a coating or layer, at marginal edge portions thereof, of minute microscopic pressure-rupturable capsules containing therewithin one or more materials which when released from said capsules provide an adhesive or bonding material or composition adapted to closely bond another photographic element with which it is superposed so as to form a substantially lighttight sandwich. An adhesive may be encasulated within minute pressure-rupturable capsules formed of a film-forming polymeric material, or the encapsulation may be dispensed with and the adhesive employed in an inactive form. When an adhesive in inactive form is employed either within or without the capsules there is also employed an activator therefor. In one embodiment, the activator is a vehicle or solvent for the adhesive and is encapsulated within minute, pressure-rupturable capsules of a polymeric material. The

activator-containing capsules may be interspersed with the adhesive which may. or may not be encapsulated or they may becarried by a photographic element which is to be brought into superposition with a photographic element carrying an adhesive-containing coating or they may form an undercoat or overcoat with an adhesivecontaining coating. The present invention also contemplates the use of a photographic assemblage comprising a photosensitive element including a photosensitive stratum and a support, an image-receiving element including an image-receiving stratum and a support, and a container of processing composition to be spread between the photosensitive stratum and the image-receiving stratum in superposed relation to provide a sandwich, at least one of the above-mentioned strata having at or near marginal edge portions thereof a coating or layer of minute pressure-rupturable capsules containing therewithin one or more materials which, when released from said capsules, provide an adhesive or binding material or composition. In one embodiment, framing means such as a mask may be secured to the surface of the image-receiving stratum and either the framing means or the photosensitive stratum may have at marginal edge portions thereof a coating of the aforementioned type. As mentioned above, the photographic assemblages described are useful in diffusiontransfer processes. In processes of this type, a photosensitive element containing a photosensitive stratum is eX- posed and a liquid processing composition is applied from a container to the photosensitive element in a substantially uniform layer as the photosensitive element is brought into superposed relationship with an image-receiving element. Spreading of the liquid processing composition from the container is accomplished by advancing the photosensitive and image-receiving elements and container between a pair of pressure-applying members such as rollers. Simultaneously with the elements being brought into superposed relationship and the processing composition being uniformly spread therebetween, an adhesive or adhesive-forming material carried by at least one of the elements is released from pressure-rupturable capsules or activated by or reacted with another material released from pressure-rupturable capsules, thus closely bonding together the edges of the elements so as to substantially exclude light from penetrating such edges into the interior of the sandwich during the processing period.

In another embodiment of the invention, a light-absorbing medium of material, such as a dye or pigment, may be utilized in conjunction with the adhesive. The lightabsorbing material may be encapsulated within minute microscopic pressure-ruptura-ble capsules formed of a film-forming polymeric material, or the encapsulation may be dispensed with and the light-absorbing material employed in an inactive form. When suchmaterial in inactive form is employed either within or without the capsules there is also employed a solvent or vehicle therefor, preferably in liquid form and encapsulated within minute, pressure-rupturable capsules of a film-forming polymeric material. The encapsulated solvent or vehicle, which may also be a solvent or vehicle for the adhesive utilized, may be interspersed with the light-absorbing material and/or adhesive which may or may not be encapsulated or the solvent or vehicle containing capsules prises a photosensitive element 10, image-receiving element 16 and a container 24 of a liquid processing composition operatively secured to element 16 or, if desired, to element 10. Photosensitive element 10 comprises a photosensitive stratum 12, e.g., a silver halide emulsion and a support 14 therefor.

Image-receiving element 16 comprises an image-receiving stratum 18 and a support 20 therefor. The imagereceiving stratum is provided with a mask 22 in the form of a sheet or layer attached to the image-receiving stratum and having an aperture therein defining the area of the image-receiving stratum in which the image can be formed. The aperture in the mask defining the imagereceiving area may be of any desired shape, being rectangular in the preferred form shown. Near or at the marginal edge portions of the mask 22 there is provided a substantially continuous'coating or layer 26 containing an adhesive or adhesive-forming material. Coating 26 may comprise capsules containing an adhesive which is of the type that, when released from the capsules, it

achieves or causes bonding without any treatment or adhesive-forming material, and the other type enclosing an activator therefor, e.g., a liquid solvent 'or medium or a catalyst or reactant. The two types of capsules may be interspersed to form a single coating or layer or they may be coated separately, one over the other, so as to form two contacting or contiguous layers or they may be carried separately, one type by the photosensitive stratum 12 and the other type by the image-receiving stratum 18 or mask 22. In one embodiment, coating 26 comprises a mixture of interspersed pressure-rupturable minute capsules of two types, one type containing a viscous, non-flowing adhesive material, and the other type containing a liquid solvent or medium for solubilizing or activating the adhesive material when the capsulesv are ruptured. Coating 26 may also comprise substantially solid, finely divided particles of an adhesive material either mixed or interspersed with capsules enclosing an activator therefor, e.g., a liquid solvent, or the adhesive particles and encapsulated activator may he maintained as distinct layers or coatings as indicated above.

The photosensitive stratum 12 is processed following exposure by supenposing the photosensitive and imagereceiving elements with the photosensitive stratum 12 and mask 22 located innermost and with container 24 located between the elements adjacent one edge of the image-receiving area defined by the aperture in mask 22. The superposed elements are then moved, commencing in the region of container 24, between a pair of pressure-applying members for rupturing the capsules and for discharging the processing composition from the container between the elements and spreading the processing composition in a thin layer between the surfaces of the photosensitive and image-receiving strata. The sandwich thus formed is allowed to imbibe for a predetermined processing period ranging, for example, from a few seconds to three minutes, during which time an image is formed in the image-receiving area. The photosensitive element, mask and preferably a layer of processiug composition are then stripped from the image-receiving element to expose the positive image formed.

Although coating 26 is illustrated as being carried at marginal edge portions of mask 22, it should be noted that it can be carried instead at or near the marginal edge portions of photosensitive stratum 12. In cases where a mask 22 is not employed, coating 26 may be carried at or near the marginal edge portions of imagereceiving stratum 18 or photosensitive stratum 12. It should again be pointed out that where both an adhesive or adhesive-forming material and an activator therefor are employed they need not be interspersed to form a single layer but that the adhesive material may be coated at the marginal edge portions of one stratum and the activator therefor may be coated on another stratum or 'both so coated on one stratum or means as to comprise an undercoat and an overcoat. For example, the adhesive either within or without capsules may be coated on mask 22 as hereinbefore indicated and the activator therefor coated at the marginal edge portions of photosensitive stratum 12, or vice versa. Alternatively, for example, the activator may be coated on mask 22 and the adhesive either within or without capsules may be overcoated thereon, or vice versa.

A light-absorbing material, such as a dye or pigment, may be incorporated in coatings 26 of the above-mentioned types so as to render the adhesive bond formed substantially opaque to actinic light and thus give additional help in preventing environmental light from penetrating the edge portions of the photographic sandwich. The light-absorbing material may be contained within its own capsules or within capsules of the types heretofore mentioned or employed in a substantially solid form which is activated or mobilized simultaneously with the adhesive. In accordance with the present invention, the light-absorptive opacifying agent or material comprises a dye or pigment which is capable of imparting substantial opacity to the sandwich edges. Thus, for example, where photosensitive stratum 12 comprises an orthochromatic silver halide stratum, the material employed should absorb or reflect light of wavelengths shorter than the wavelengths of red and where photosensitive stratum 12 comprises a panchromatic silver halide stratum, the material should absorb visible and near-visible light of all wavelengths. The light-absorbing material may be an organicdye, for example, a black dye sold by du Pont under the trade name Rayon Black GFN (CI. 619) or sold by National Aniline Division of Allied Chemical and Dye Corporation under the trade names Erie Black BF (Cl. 581), Erie Black RF (Cl. 582) and National Buffalo Black NBR, High Conc. or a red dye sold by du Pont under the trade name .Congo Red (0.1. 370), sold by National Aniline under the trade name Erie Scarlet B (CL 382), or by General Dyestulf Corporation under the trade name Congo Corinth GA-EXCF (Cl. 375). Other watersoluble and oil-soluble organic dyes may be employed in addition to the above mentioned. Alternatively, the lighta-bsorbing material is a pigment, for example, a black solid such as carbon or colloidal graphite which absorbs all visible or near-visible wavelengths. The preferred dyes and pigments may be utilized in substantially solid or viscous form, in which case they are dissolved or dispersed in a suitable solvent or vehicle therefor released from pressure-rupturable capsules. Alternatively such dyes and pigments may be dissolved or suspended in a suitable solvent or vehicle therefor and carried in this mobile or flowable form within pressure-rupturable capsilles. The use of a light-absorbing material in the above manner thus renders opacity to the adhesive bond pro duced at the marginal edge portions of the sandwich without covering the imageor print-forming areas.

As indicated previously, the supports of the photosensitive and image-receiving elements should be opaque, Specific supports may comprise black papers or a plastic containing a dispersed black pigment, aluminum coated papers, etc., or any of the supports shown, for example, in the aforementioned US. application Serial No. 825,754. The opaque surfaces or light barriers should provide sufficient shielding of the photosensitive stratum so that no fogging or desensitization thereof occurs due to light leakage or penetration through the protective sandwich surfaces during the processing period even in bright natural or artificial light.

The present invention is applicable to a variety of processes and products involving the formation of latent images in dispersions of heavy metal salts such as the noble metal salts, particularly the silver halides. It is particularly applicable to processes of the silver transferreversal type described in US. Patent No. 2,543,181, issued to Edwin H. Land on February 27, 1951. In such a process, a photo-exposed silver halide is treated between two elements by a silver halide developer and a silver halide solvent. The reagents reduce exposed silver halide to silver and react with unreduced silver halide to form a soluble silver complex which, in turn, is reduced to silver in a silver-receptive environment.

In one form of silver halide stratum, one or more of the silver, halides, of which silver chloride, silver bromide and silver iodide are examples, are dispersed in a protective colloid material, for example, gelatin, agar, albumen, casein, collodion, a cellulosic such as carboxymethyl .cellulose, a vinyl polymer such as polyvinyl alcohol, or a linear polyamide such as polyhexamethylene adipamide. Examples of specific formulations of conventional emulsions suitable for such use are described in T. T. Baker, PhOtOgraphiC Emulsion Techniques, American Publishing Company, Boston (1948), chapter IV.

The image-receptive stratum provides one of the vigorous silver precipitating environments described in US. Patents Nos. 2,698,237 and 2,698,245 issued to Edwin H. Land on December 28, 1954. Such an environment includes silver precipitating nuclei such as the heavy metal sulfides and/or selenides, the collodial noble metals, or organic thio compounds dispersed in a macroscopically continuous vehicle comprising a water-permeable, inorganic, preferably siliceous, material. This material may contain, in colloidal or finely divided condition, oxides of silicon, particularly those in the form of silicic acids like slica aerogel, and mineral silicates such as mica and talc. Preferably, the image-receptive stratum is from 1 to 8 microns thick.

Preferred paper base materials for the mask comprise sulfate kraft fiber, preferably condenser tissue paper, highporosityrope fiber, and heat-conductive paper base stock, preferably having a thickness of from 0.00l of an inch to 0.003 of an inch. However, it must be noted that synthetic materials, as for example, regenerated cellulose or cellophane or a thin polyester sheet, as for example, Mylar (registered trademark of E. I. du Pont de Nemours & Co., Wilmington, Delaware, for a film of polyethylene terephthalate resin), preferably having a thickness of approximately 0.0008 of an inch, comprise highly advantageous masking materials especially where it is desired that the laminae thickness be decreased and an edge tear strength in excess of that obtained by conventional paperbased masking materials be afforded. Such characteristics are especially desirable in pressure stripping methods. Other flexible sheet materials may be employed to provide mask 22.

The sealing of mask 22 to image-receiving stratum 18 results in a substantially complete and uniform bonding of the apposed strata, in contact therewith, possessing sufficient strength to hold mask 22 fiat and smooth on the surface of the image-receiving stratum 18 during the manufacture, storage and use of the product until such time as mask 22 and image-receiving stratum 18 are to be separated.

The preferred seal exhibits wet strength failure upon contact of said bond with a liquid, that is, a linear reduction of the adhesive force according to the degree of liquid permeation. It is especially desirable that the aforementioned bond be one in which substantially complete release of the adhesive capacity between the respective mask and image-receiving strata occurs within the desired optimum photographic processing interval for each of the various diffusion-transfer processes.

It has been found that the utilization of a moisturerelease system results in a remarkably clean separation when the print section 12 of the print-receiving element 10 is removed from contact with the mask 22. The separation of the print section 12 from contact with the mask 22 by reduction of the adhesive force has the singu lar advantage in that there is exhibited no tendency for laceration of the print section 12 occurring due to variances in the adhesive binding forces inherent in pressure stripping methods.

Suitable developers for liquid processing compositions are: benzene derivatives having at least two hydroxyl and/or amino groups substituted in ortho or para position on the benzene nucleus, such as hydroquinone, Amidol, Metol, glycin, p-aminophenol and pyrogallol; and hydroxylamines, in particular primary and secondary aliphatic and aromatic N-substituted or B-hydroxylamines which are soluble in aqueous alkali, including hydroxylamine, N-methyl hydroxylamine, N-ethyl hydroxylamine and others described in US. Patent No. 2,857,276. Suitable silver halide solvents are: conventional fixing agents such as sodium thiosulfate, sodium thiocyanate, ammonium thiosulfate and others described in U.S. Patent No. 2,543,181, supra; and associations of cyclic imide and nitrogenous bases such as associations of barbiturates or uracils, and ammonia or amines, and other associations described in US. Patent No. 2,857,274. Preferably, the solution also contains a film-forming material such as a water-soluble polymer, starch or gum for imparting a viscosity of to 200,000 centipoises at a temperature of 20 C.

In lieu of rendering the adhesive bond at the edges of the sandwich opaque, the processing composition may contain a light-absorptive opacifying agent such as a black or red dye or pigement (e.g. colloidal graphite) so as to render the layer of processing composition between the photosensitive and print-receiving elements opaque to actinic light. The use of such opacifying agents in the processing composition is more fully described in the copending US. application of Edwin H. Land, Serial No. 537,349, filed September 29, 1955, now abandoned.

Container 24, in one form, is constructed from a blank of three-ply sheet material having a single fold. The outer ply serves as a backing or support and is composed of a thin, relatively inexpensive, tough material, preferably a paper, such as kraft paper. The intermediate ply is composed of a substantially vaporand liquidimpervious material, for example a metal foil such as aluminum or lead foil. The inner ply is composed of a thermoplastic or thermosetting plastic materialQfor example polyvinyl chloride or a polyvinyl acetal suchas polyvinyl butyral or polyvinyl formal, which protects the container contents from contamination. At opposite end portions of the container, the two folds of the inner ply are sealed to each other by the application of heat and pressure. Those two sections of the two folds defining a month are bonded together by a strip of adhesive so constituted that the bonding forces between it and the inner ply are less than the cohesive forces between end portions of the inner ply that are sealed together. A satisfactory strip may be composed, for example, of ethyl cellulose or a mixture of ethyl cellulose and paraffin, the mixture including at least 50% by weight of ethyl cellulose. Since the bonding forces between those sections defining the mouth are less than the bonding forces between other sections of the container, the application of opposed compressional forces to the container causes discharge of the containers contents through its mouth.

The proportions of the ingredients of the processing composition may be varied within wide limits. However, where the processing period is, as specified, within the range of from a few seconds to seconds, in accordance with the now conventional duration of silver transferreversal processing periods, practical results are achieved where, in concentration, by total weight of the solution, the developer ranges from 1% to 8% and the solvent from 0.3% to 10%.

Although the present invention has been described above in relation to silver transfer-reversal processes, it is to be understood that it may be applied to other photo graphic black-and-white, as well as color, processes. For example, where a ferric salt, diazonium compound or bichromated colloid is dispersed as a photosensitive stratum on one of a pair-of sheets, the processing composition to be spread between the sheets in order to produce a print is a coupler that differentiates between exposed and unexposed ferric salt to form a visible reduction product, a coupler that differentiates between exposed and unexposed diazonium compound to form a visible dye, or a visible medium that is differentially absorbed by differentially hardened colloid. The present invention may also be applied to color processes such as described, for example, in U.S. Patents Nos. 2,559,643, 2,698,798 and 2,774,668 and in copending U.S. applications Serial No. 748,421, filed July 14, 1958, now U.S. Pat. No. 2,983,606 and Serial No. 565,135, filed February 13, 1956.

The minute capsules of the present invention may be formed of pressure-rupturable film-forming polymeric material of a hydrophilic nature or character such as, for example, gelatin; or they may be formed of pressurerupturable film-forming polymeric material of a hydrophobic nature such as, for example, polyvinyl chloride.

- Each capsule consists of a nucleus comprising, for example, adhesive or adhesive-forming material or activator around which has been deposited a dense shell-like coating of pressure-rupturable film-forming polymeric material. The capsule coatings preferably comprise, in substantial contiguity, a profuse number of capsules of pressure-rupturable polymeric material of minute size.

The encapsulating material which encloses or surrounds the nucleus may comprise one or more hydrophilic filmforming polymeric materials or one or more film-forming hydrophobic polymeric materials or mixtures thereof. Thus, hydrophilic polymeric materials such as gelatin, gum arabic, methyl cellulose, starch, alginates, polyvinyl alcohol, casein, agar-agar and the like may be utilized as encapsulating materials. It is also possible to employ as the encapsulating material a complex of film-forming hydrophilic polymeric materials. By a complex of hydrophilic polymeric materials is meant the product resulting from the union in a suitable medium of two kinds of hydrophilic polymeric materials having opposite ionic charges in said medium, the union being brought about by such difference in charge. Hydrophobic polymeric materials such as, for example, polyvinyl chloride, buta-.

ployed and the particular material to be encased there-' within.

There are many ways in which the capsules of the present invention may be formed and which are Well known to the art. Suitable methods are described, for example, in U.S. Patents Nos. 2,800,457, 2,800,458 and 2,907,682. One illustrative method of making minute or microscopic capsules of hydrophilic polymeric material containing an adhesive comprises making an aqueous sol of a hydrophilic polymeric material, e.g., gelatin, and emulsifying therein a water-immiscible organic liquid, e.g., chlorinated diphenyl, in which the adhesive, e.g., chlorinated rubber, is dissolved or stability suspended until the required microscopic drop size is attained, and thereafter diluting the emulsion with water or an acidified aqueous solution in such amount as to cause the hydrophilic polymeric material to deposit around each microscopic drop of ad hesive. All of the foregoing steps are carried out at a temperature above the gelatin or solidification point of the polymeric material. In the case of gelatin, the temperature during these steps is maintained at 50 C. or above. Gelation or solidification of the encapsulating material is then achieved by cooling to a temperature below the gelation or solidification point of the material. If this latter step is performed rapidly, as by rapid cooling, the

pore size of the resultant'capsules will be small. If the gelation step is performed slowly, the pore structure of the encapsulating material will be coarser. At this point the encapsulation of the adhesive with hydrophilic poly- 1'0 meric material is complete, and any further steps are to put it in condition for the intended use.

If it is desirable to make the capsular material, as produced above, hard, more heat resistant and insoluble in water, it can be treated, for example, with a well known gelatin hardener, e.g., formaldehyde and the like. If desired, after hardening and drying, the agglomerate mass of capsules may be comminuted to form fine granules of any desired size.

An illustrative method of making capsules of two hydrophilic polymeric materials such as gelatin and gum arabic comprises forming two compatible sols by dispersing hydrophilic materials such as gum arabic and gelatin in water, mixing the two aqueous sols together and then emulsifying therein the water-immiscible organic liquid and adhesive or emulsifying the organic liquid and adhesive in one of the sols first and then mixing the emulsion with the second sol. The pH of the emulsion so formed, if necessary, may be adjusted so that the ions of the two materials, e.g., gum arabic and gelatin, have different electric charge. Deposition of a complex of hydrophilic materials around microscopic nuclei or droplets of the water-immiscilble organic liquid containing an adhesive is achieved by dilution with water and/or changing the pH of the mixture. All of the foregoing steps are carried out at temperatures above the gelatin or solidification point of the hydrophilic polymeric material. Gelation is achieved as previously described, that is, by cooling the complex encapsulating material below its gelatin or solidification temperature.

Activator-containing capsules may be prepared by similar methods. For example, adhesive solvent-containing capsules may be made by emulsifying the solvent, e.g., petroleum distillate, in a gum-arabic-gelatin-in-water solution and after the desired drop size is achieved, diluting the emulsion with water and lowering the pH so that the gelatin-gum-ar-abic complex will deposit around the solvent droplets as a liquid phase, which is gelled and hardened as previously described.

Another encapsulation method known to the art comprises feeding or extending a film-forming encapsulating material in viscous liquid form into a nozzle where it forms a membrane over the nozzles orifice and introducing into such membrane, through a tube-leading to the orifice, a filler material, e.g., adhesive or activator. In one embodiment the film-surrounded filler separates into minute capsules by gravitational and surface tension forces. In another embodiment the film-surrounded filler is ejected from the nozzle by centrifugal force. In each case minute capsules so formed are dropped or flung into a suitable bath to cause hardening or setting of the encapsulating film-forming material.

As mentioned previously, adhesives which may be employed are well known in the art. For example, there may be employed pressure-sensitive adhesives, solventresponsive adhesives, chemicallyreactive adhesives and the like. Pressure-sensitive adhesives function immediately upon application without any physical or chemical change in the adhesive; in other words, they provide instantaneous adhesive when applied under light pressure. Pressure-sensitive adhesive compositions may comprise rubber, polyisobutylene, acrylic and methacrylic polymers, vinyl polymers, allyl resins and the like. With solvent-responsive adhesives, adherence during bonding is effected by means of a liquid carrier which evaporates or is absorbed. Such adhesives may comprise compositions including acrylate and methacrylate polymers, alkyd resins, cellulose ethers or esters, natural resins as shellac and rosin, vinyl polymers, rubber or synthetic rubbers, vegetable gums and starches and protein glues. carrier generally comprises a solvent for the adhesive. Chemically reactive adhesives, i.e., those which undergo chemical change during formation of the bond, e.g., crosslinking, condensation polymerization, etc., may also be employed. The term activator, or similar expressions The liquid as used herein, includes within its meaning materials for physically and/or chemically activating adhesive materials, e.g., solvents or vehicles for solubilizing or carrying adhesive materials, reactants,- catalysts and the like necessary to efiect chemical reaction such as polymerization, etc.

As indicated previously, the adhesive to be employed may be so chosen as to give either temporary or substantially permanent bonding. Thus, when the marginal edge portions of the photosensitive and image-receiving strata are to be directly bonded together for the processing period and then separated or stripped apart, the adhesive employed should be one which gives ready and easy separation without lacerating the image-receiving stratum, e.g., moisture-releasable adhesives. When the marginal edge portions of the photosensitive stratum and framing means are to be bonded together, the adhesive employed is preferablyone which gives a good bond so that the photosensitive element and framing means may be stripped or separated together from the image-receiving stratum.

Since certain changes may be made in the above processes and products without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In a photographic product including a photosensitive element comprising a photosensitive stratum and a substantially opaque support therefor; an image-receiving element comprising an image-receiving stratum and a substantially opaque support therefor, said strata being adapted to be positioned in face-to-face relationship for processing at some time subsequent to exposure of said photosensitive element; and a rupturable container positioned between said strata and having therein a photographic processing composition for spreading between said strata when in face-to-face relationship to provide a sandwich in which a visible image is formed during a predetermined processing periodythe improvement which comprises providing a coating on the periphery of at least three sides of the facing surface of at least one of said elements, said coating containing a profusion of substantially contiguous minute pressure-rupturable capsules formed of a polymeric film-forming material having encapsulated therein at least one material which, when released from said capsules, provides an adhesive capable of bonding together superposed marginal edge portions of said sandwich during said processing period, said adhesive material also permitting separation of said elements after said processing period.

2. A photographic product as defined in claim 1 wherein said image-receiving element contains a mask adhered over portions of. said image-receiving stratum, said mask defining a picture area on said image-receiving stratum; said coating of pressure-rupturable capsules being on at least one of said photosensitive stratum and said mask whereby to permit bonding together of superposed marginal edge portions of said mask and said photosensitive element during said processing.

3. A photographic product as defined in claim 1 wherein said encapsulated material comprises an activator for an adhesive-forming material in a coating along the periphery of at least three sides of one of said elements, said activator comprising a vehicle for said adhesive-forming material.

4. A photographic product as defined in claim 1 wherein at least one of said elements contains along the periphery of at least three sides thereof a light-absorbing material selected from the group consisting of red and black dyes and pigments.

5. A photographic product as defined in claim 4 wherein at least one of said light-absorbing materials and a solvent therefor is encapsulated.

6. In a photographic product including a photosensitive element comprising a photosensitive stratum and a substantially opaque support therefor; an image-receiving element comprising a substantially opaque support having thereon, an image-receiving stratum and a mask along the periphery of and defining a picture area on said imagereceiving stratum, said strata being adapted to be positioned in face-to-face relationship for processing at some time subsequent to exposure of said photosensitive element; and a rupturable container positioned between said strata and having therein a photographic processing composition for spreading between said strata when in faceto-face relationship to provide a sandwich in which a visible image is formed during a predetermined processing period; the improvement which comprises providing a substantially continuous coating on the periphery of the facing surface of at least three sides of at least one of said photosensitive stratum and said mask, said coating containing a profusion of substantially contiguous microscopic pressure-rupturable capsules formed of a polymeric film-forming material having encapsulated therein at least one material which, when released from said capsules, provides an adhesive for bonding together superposed marginal edge portions of said sandwich during said processing period, said coating containing said capsule being located without said picture area, said bonding material also permitting separation of said elements after said processing period.

7. A photographic process comprising the steps of advancing, into superposition, a photoexposed photosensitive stratum and an image-receiving stratum having a mask thereon defining a picture area, with a thin layer of a photographic processing composition interposed substantially uniformly between said strata, to form a sandwich; substantially simultaneously rupturing a coating containing a profusion of substantially contiguous minute capsules formed of a polymeric film-forming material and carried on the periphery of at least three sides of at least one of said' photosensitive stratum and said mask, said capsules having encapsulated therein at least one material which, when released from said capsules, bonds together superposed marginal edge portions of said sandwich during said processing, and separating said image-receiving stratum from said photosensitive stratum after said processing period to provide a visible image.

References Cited by the Examiner UNITED STATES PATENTS 409,618 8/1889 Spiro 9662 787,103 4/1905 Ludwig 9662 2,543,181 7 2/1951 Land 9629 2,609,296 9/ 1952 Land 9676 2,627,460 2/1953 Land 9676 2,653,530 9/1953 McCune 9629 2,800,457 7/1957 Green 11736.1 2,834,269 5/1958 Land 9676 2,834,271 5/ 1958 Booth 95-67 2,907,682 10/ 1959 Eichel 117-21 2,909,977 10/1959 Eburn 9676 2,988,461 6/1961 Eichel 117'36.1 3,001,873 9/ 1961 Foris 9629 3,016,308 1/1962 Macaulay 11736.1 3,037,670 6/ 1962 Erlichman 222 FOREIGN PATENTS 571,322 8/1945 Great Britain. 825,146 12/ 1959 Great Britain.

NORMAN G. TORCHIN, Primary Examiner.

PHHJIP E. MANGAN, Examiner.

G. H. BJORGE, A. E. TANENHOLTZ, D. LEVY,

Assistant Examiners. 

1. IN A PHOTOGRAPHIC PRODUCT INCLUDING A PHOTOSENSITIVE ELEMENT COMPRISING A PHOTOSENSITIVE STRATUM AND A SUBSTANTIALLY OPAQUE SUPPORT THEREFOR; AN IMAGE-RECEIVING ELEMENT COMPRISING AN IMAGE-RECEIVING STRATUM AND A SUBSTANTIALLY OPAQUE SUPPORT THEREFOR, SAID STRATA BEING ADAPTED TO BE POSITIONED IN FACE-TO-FACE RELATIONSHIP FOR PROCESSING AT SOME TIME SUBSEQUENT TO EXPOSURE OF SAID PHOTOSENSITIVE ELEMENT; AND A RUPTURABLE CONTAINER POSITIONED BETWEEN SAID STRATA AND HAVING THEREIN A PHOTOGRAPHIC PROCESSING COMPOSITION FOR SPREADING BETWEEN SAID STRATA WHEN IN FACE-TO-FACE RELATIONSHIP TO PROVIDE A SANDWICH IN WHICH A VISIBLE IMAGE IS FORMED DURING A PREDETERMINED PROCESSING PERIOD; THE IMPROVEMENT WHICH COMPRISES PROVIDING A COATING ON THE PERIPHERY OF AT LEAST THREE SIDES OF THE FACING SURFACE OF AT LEAST ONE OF SAID ELEMENTS, SAID COATING CONTAINING A PROFUSION OF SUBSTANTIALLY CONTIGUOUS MINUTE PRESSURE-RUPTURABLE CAPSULES FORMED OF A POLYMERIC FILM-FORMING MATERIAL HAVING ENCAPSULATED THEREIN AT LEAST ONE MATERIAL WHICH, WHEN RELEASED FROM SAID CAPSULES, PROVIDES AN ADHESIVE CAPABLE OF BONDING TOGETHER SUPERPOSED MARGINAL EDGE PORTIONS OF SAID SANDWICH DURING SAID PROCESSING PERIOD, SAID ADHESIVE MATERIAL ALSO PERMITTING SEPARATION OF SAID ELEMENTS AFTER SAID PROCESSING PERIOD. 